This invention relates to gas-fired cooking ranges and particularly to a cooktop for domestic gas ranges which provides high thermal efficiency and low emissions of air pollutants such as carbon monoxide (CO) and oxides of nitrogen (NO.sub.x).
Conventional domestic gas-fired cooking ranges typically operate with thermal efficiencies of about 45 percent and produce small amounts of CO and NO.sub.x. The carbon monoxide is produced because combustion efficiency is incomplete, and oxides of nitrogen are generated in reactions caused mainly by the presence of high temperatures in the burner flame. Although some studies have indicated that there is no evidence that gas cooking is a health hazard, other researchers in the area of indoor air pollution have claimed that levels of CO and NO.sub.x in gas kitchens are of concern.
A gas range which avoids the above-mentioned indoor pollutants is disclosed in U.S. Pat. No. 2,870,829. In that range, burning occurs in an enclosed combustion chamber beneath a plate of heat-resistant glass or ceramic which supports a cooking utensil, and flue products can readily be ducted outside the building without discharging pollutants into the kitchen. Another smooth-top range is described in U.S. Pat. No. 4,020,821; that range may, however, discharge diluted flue products into the kitchen area after collection. Although these smooth-top gas ranges can readily avoid contributing to indoor pollution, their thermal efficiencies may be relatively low. Also, their glass-ceramic tops may be less durable and safe than desired, and the extensive ducting of these ranges may result in packaging problems and high manufacturing costs.
Accordingly, it is an object of the invention to provide a gas-fired cooktop with high thermal efficiency.
It is an object of the invention to provide a gas-fired cooktop which, in addition to operating at high thermal efficiency, discharges NO.sub.x at levels sufficiently low so as not to significantly contribute to indoor pollution.
It is an object of the invention to provide a cooktop for a residential gas range which, in addition to the above objects, is of simple construction, has good thermal shock resistance, and is easy to clean and attractive in appearance.